Power supply fan management

ABSTRACT

A power supply includes a casing; an AC-to-DC converter; an inverter electrically coupled to the AC-to-DC converter; a transformer having a primary side and a secondary side, wherein the inverter is electrically coupled to the primary side of the transformer; an output rectifier electrically coupled to the secondary side of the transformer; a fan, disposed in the casing and configured to remove heat from the casing generated by the AC-to-DC converter, the inverter and the output rectifier; and a fan controller configured to control when the fan is operational, wherein the fan controller is configured to execute a state machine that is configured to change states based at least on a dynamically adjustable counter.

FIELD OF THE DISCLOSURE

The present disclosure is directed to welding and cutting equipment and,more particularly, to techniques for controlling the operation of acooling fan integrated with a power supply for welding and cuttingequipment.

BACKGROUND OF THE DISCLOSURE

A power supply designed for welding or cutting includes an input-sideAC-to-DC converter which converts a commercial AC voltage to a DCvoltage. The DC voltage is applied to an inverter where it is convertedto a high-frequency voltage, which, in turn, is applied to a voltagetransformer. The voltage transformer transforms the high-frequencyvoltage to a high-frequency voltage having a predetermined value. Thevoltage-transformed high-frequency voltage from the transformer isconverted back to a DC voltage in an output-side high-frequency-to-DCconverter, e.g., a rectifier. The resulting DC voltage is applied to aload, e.g., a torch that operates near a workpiece.

The input-side AC-to-DC converter and the output-sidehigh-frequency-to-DC converter (e.g., rectifier) each includes at leastone diode. The inverter includes at least one semiconductor switchingdevice, such as an IGBT.

Since the power supply includes an inverter, the power supply can employsmaller-sized reactors in the transformer and the output-sidehigh-frequency-to-DC converter, enabling the downsizing of the powersupply.

Such a downsized power supply can be disposed in a single casing.Although such a casing provides an aesthetically pleasing package, Jouleheat generated by the aforementioned components tends to accumulate inthe casing. In particular, the diodes used in the input-side andoutput-side AC-to-DC converters and the power semiconductor devices usedin the inverter, generate a large amount of heat. Typically, a fan isdisposed in the casing for the purpose of forcibly cooling such devices.

Fan operation in a welding power source, however, can introduce severalnegative by-products including (1) noise pollution in the work place,(2) increased dust accumulation inside the casing thereby impactingservice life, and (3) increased wear on the fans themselves also causingdecreased service life.

SUMMARY OF THE DISCLOSURE

A power supply includes a casing; an AC-to-DC converter; an inverterelectrically coupled to the AC-to-DC converter; a transformer having aprimary side and a secondary side, wherein the inverter is electricallycoupled to the primary side of the transformer; an output rectifierelectrically coupled to the secondary side of the transformer; a fan,disposed in the casing and configured to remove heat from the casinggenerated by the AC-to-DC converter, the inverter and the outputrectifier; and a fan controller configured to control when the fan isoperational, wherein the fan controller is configured to execute a statemachine that is configured to change states based at least on adynamically adjustable counter.

In another embodiment, a method is provided. The method includesdetecting an arc powered by a power supply; incrementing a counter whilethe arc is being detected; determining whether a value of the counter isgreater than a predetermined threshold; and when the value of thecounter is greater than the predetermined threshold, turning on a fan toremove heat from a casing of the power supply.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, embodiments of the disclosed systems and methods willnow be described, with reference to the accompanying drawings, in which:

FIG. 1 depicts a block diagram of a power supply for a multi-processwelding and cutting machine including a fan and fan control logic foroperating the fan in accordance with an example embodiment.

FIG. 2 depicts a state machine implemented by the fan control logic inaccordance with an example embodiment.

FIG. 3 is a flow chart illustrating a series of operations forcontrolling a fan in a power supply for a multi-process welding andcutting machine in accordance with an example embodiment.

DETAILED DESCRIPTION

FIG. 1 depicts a block diagram of a power supply for a multi-processwelding and cutting machine including a fan and fan control logic foroperating the fan in accordance with an example embodiment.Specifically, power supply 100 includes an AC-DC converter 110 connectedto an inverter 112, which is connected to a primary side of atransformer 114. A secondary side of the transformer 114 is connected toa rectifier 116, which provides an output of the power supply.

A memory 120, which stores fan control logic 200, is in communicationwith a processor 130. The processor 130 may control a switch 140 that isused to control the operation of a fan (or fans) 150, by allowingelectrical current to flow to a motor of the fan (not shown). Thecomponents described above are all mounted inside a casing 105, and thefan 150 itself is mounted in such a way so as to, when in operation,circulate ambient air inside the casing 105, thereby cooling thecomponents that generate heat. The combination of the memory 120, fancontrol logic 200, processor 130, and switch 140 maybe collectivelyreferred to as a fan controller 180. A current sensor 118 may provide,to processor 130, an indication of whether, e.g., weld current isflowing out of power supply 100, and which indication may be anindication of a welding or cutting (hereafter “welding” arc beingpresent between a torch and a workpiece.

The processor 130 may include one or more processing units that areconfigured to load instructions (e.g., fan control logic 200) frommemory 120. The memory 120 may include read only memory (ROM), randomaccess memory (RAM), magnetic disk storage media devices, opticalstorage media devices, flash memory devices, electrical, optical, orother physical/tangible memory storage devices. In general, the memory120 may include one or more tangible (non-transitory) computer readablestorage media (e.g., a memory device) encoded with software or firmwarecomprising computer executable instructions, and when the instructionsare executed (by the processor 130) they are able to perform theoperations described herein.

In accordance with an embodiment, and at a high level, fan controller180, which may implement a state machine, is configured to manage theoperation of fan 150 using a dynamically adjustable counter (or simply“counter”), and an indication of the presence of a welding arc in such away so as to minimize the fan's operation time without appreciablyaffecting the thermal quality of the system or the life of theelectronic components that comprise the power supply 100. The term “arc”or “welding arc” is also meant to include an arc used for cutting orgouging. In accordance with one implementation, the fan controller 180delays turning on the fan 150 until weld current has been detected for along enough duration of time, to establish that a committed workscenario has commenced.

In this regard, the techniques include, depending on a state of thestate machine, incrementing the counter, on a time-element-schedule(e.g., second(s) or fractions thereof), or decrementing the counter on atime-element-schedule (e.g., second(s) or fractions thereof). Theoperations of incrementing and decrementing the counter may be sloweddown or sped up by applying one or more multipliers, depending of thestate of the state machine. If the counter is above a given threshold,the switch 140 is controlled to cause fan 150 to operate.

For example, the counter may be incremented in real time, e.g., anincrement of one per second, but decremented at one third that speed,i.e., the counter is decremented by one for each 3 seconds of elapsedtime.

In an embodiment, after the welding action has completed (i.e., an arcis no longer detected), the fan controller 180 may be configured toprovide a fan ‘on’ condition until the counter decrements to zero. If awelding arc is detected before the counter reaches zero, the counter isagain incremented. Notably, the described implementations forcontrolling the operation of a fan do not rely on thermal detection.Rather, fan operation is tied to a value of a counter, and the counteris incremented or decremented as explained above, and in more detailbelow in connection with FIG. 2.

FIG. 2 depicts a state machine implemented by the fan control logic 180in accordance with an example embodiment. The state machine of FIG. 2includes a fan OFF state 210 and a fan ON state 220. The fan OFF state210 includes two sub-states including an idle state 212 and await_arc_time state 214. The fan ON state 220 includes two sub-statesincluding a fan_arc state 222 and a fan_cooling state 224.

In idle state 212, the fan 150 is off, no welding arc is detected, and avalue of a counter 290 is zero. That is, the idle state 212 may beconsidered the state at which the welding power supply 100 is initiallyturned on, no incrementing or decrementing of the counter 290 hasoccurred (or is occurring) and no welding (or cutting) has yet takenplace. As will be more fully understood from the discussion below, thestate machine can transition from the idle state 212, but return to thatstate at a later time.

In the weight_arc_time state 214, the fan 150 is off, and a value of thecounter is greater than zero, but below a predetermined threshold. Thecounter is incremented while a welding arc is detected, and decrementedwhen no welding arc is detected.

In the fan arc state 222, the fan is on, the counter is greater thanzero, a welding arc is detected and the counter is above zero. Thecounter may be incremented on a one-to-one basis (e.g., one secondequals one increment to the counter) or using a multiplier where thecounter is incremented more than, or less than, once for each second,for example.

In the fan_cooling_state 224, the fan is on, the counter is above zero,a welding arc is not detected, and the counter is decremented.Decrementing can proceed on a one-to-one basis (e.g., one second equalsone decrement to the counter) or using a multiplier where the counter isdecremented less than or more than once for each second, for example.

FIG. 2 also shows state transition numbers 1-7. Each state transitionnumber and its corresponding description is set forth below.

1. Fan system initialized.

2. Arc detected.

3. Counter reaches zero.

4. Counter exceeds fan start threshold.

5. Arc extinguished (i.e., no longer detected).

6. Arc detected.

7. Counter reaches zero.

The following is an example of operations of the state machine shown inFIG. 2 employing the state transitions 1-7. At state transition number1, the power supply 100 is, e.g., turned on for the first time, causingthe state machine to be placed into the idle state 212. When a weldingarc is detected at state transition number 2, the state machinetransitions to the wait_arc_time state 214. Fan control logic 200 maybecome aware of a welding arc by, for example, monitoring the outputcurrent of the power supply, receiving a torch trigger state, monitoringone or more voltages of the power supply, receiving an indication fromother logic being executed by processor 130, and/or monitoring theconsumption of power by the power supply itself, delivery of power.

In the wait_arc_time state 214, and while an arc continues to bedetected, the counter begins to increment in accordance with apredetermined time-based periodicity. For example, the counter maybeincremented by one for each second that elapses while in thewait_arc_time state 214. It is noted that how quickly the counter isincremented may also be dependent on how much power is being supplied bythe power supply. For example, fan controller 180 may be configured tomonitor output current and voltage of the power supply 100 and increasea value of a multiplier used to accelerate the counter in thewait_arc_state. Such a multiplier may be a first order multiplier, ormay be a second order multiplier. In the latter case, the first ordermultiplier might be based on geographic area, e.g., typical ambienttemperature, and/or mains input voltage.

Also, while still in wait_arc_time state 214, if the welding arc is nolonger detected, the counter begins to be decremented. Decrementing thecounter may be at the same rate as the rate the counter was incrementedwhile the arc was being detected, or may be at a different rate. If thecounter reaches zero while in the wait_arc_time state 214, then statetransition number 3 causes the state machine to move back to the idlestate 212.

However, if the counter reaches and/or exceeds the fan start thresholdvalue, then at state transition number 4, the state machine transitionsto fan_arc state 222. During the fan_arc state 222 the fan 150 is turnedon and the counter continues to be incremented either according to aone-to-one ratio with the time-based periodicity, or in accordance witha predetermined multiplier (which could be greater than or less than 1,and may be dynamically adjustable).

When the welding arc is no longer detected, then state transition number5 causes the state machine to transition to fan_cooling state 224.During the fan_cooling state 224 the counter is decremented eitheraccording to a one-to one ratio with the time-based periodicity, or inaccordance with a predetermined multiplier (which could be greater thanor less than 1).

If a welding arc is reignited, i.e., a welding arc is (again) detected,then state transition number 6 causes the state machine to move back tofan_arc state 222.

On the other hand, if while in the fan_cooling state 224 the counterreaches zero, then state transition number 7 returns the state machineto idle state 212.

Thus, as one of ordinary skill in the art will appreciate, when thepower supply is first turned on, but no welding is yet taking place, thecounter is idle, and no incrementing or decrementing occurs. However,once welding begins the counter begins to increment, but the fan is notyet turned on. Such a sequence of events accounts for a scenario inwhich a very short weld might take place that does not warrant operationof the fan. On the other hand, after some predetermined amount of time,i.e., when the counter reaches a fan start threshold value, the fan isturned on and the counter is either incremented while the welding arc isdetected or decremented while the welding arc is no longer detected. Ifthe counter eventually reaches zero while in the fan ON state 220, thefan will be turned off and the state machine will be returned to theidle state 212.

In accordance with an embodiment, the fan start threshold value (abovewhich state machine transitions to the fan ON state 220), and theincrementing and decrementing multipliers may all be adjustable, andneed not be the same in each state. For example, a decrementingmultiplier used in the wait-arc_time state 214 may cause the counter todecrement more slowly than the decrementing that occurs in thefan_cooling state 224.

The values selected for the fan start threshold and the respectiveincrementing and decrementing multipliers may be established uniquelyfor individual cases, e.g., rated power of the power supply, and/orgeographic location of operation (i.e., cooler or warmer climates).These values may also be adjustable in the field, or at least by aservice technician.

FIG. 3 is a flow chart illustrating a series of operations forcontrolling a fan in a power supply for a multi-process welding andcutting machine in accordance with an example embodiment. The sequenceof operations may be considered as one possible sequence of transitionsthrough the states of the state machine of FIG. 2.

Referring to FIG. 3, the sequence starts with 302 at which an arc isdetected. At 304, a counter is incremented without turning on the fan ofthe power supply. At 306, it is determined whether the counter is at afan start threshold. If not, the sequence returns to operation 304. Ifthe counter has reached the fan start threshold at 306, then, at 308,the fan is turned on.

At 310, the counter is incremented. At 312, it is determined whether awelding arc is detected. If yes, then the counter continues to beincremented. If the welding arc has been distinguished, then, at 312,the welding arc is no longer detected and, at 314, the counter isdecremented. At 316, it is again determined whether the arc is detected.If yes, then the sequence returns to operation 310. If the welding arcis no longer detected, it is determined, at 318, whether the counter hasreached zero. If not, the sequence returns to 314 where the countercontinues to be decremented.

If the counter has, in fact, reached zero at 318, then, at 320, the fanis turned off and the sequence returns to operation 302 where the systemis effectively in the idle state 212 shown in FIG. 2.

Thus, those skilled in the art will appreciate that the counter-basedfan management described herein need not rely on thermal sensors, andcan provide improved fan management beyond a simple on/off control tiedto, e.g., detection of weld current, no matter how little.

The above description is intended by way of example only. Variousmodifications and structural changes may be made therein withoutdeparting from the scope of the concepts described herein and within thescope and range of equivalents of the claims.

What is claimed is:
 1. A power supply, comprising: a casing; an AC-to-DCconverter; an inverter electrically coupled to the AC-to-DC converter; atransformer having a primary side and a secondary side, wherein theinverter is electrically coupled to the primary side of the transformer;an output rectifier electrically coupled to the secondary side of thetransformer; a fan, disposed in the casing and configured to remove heatfrom the casing generated by the AC-to-DC converter, the inverter andthe output rectifier; and a fan controller configured to control whenthe fan is operational, wherein the fan controller is configured toexecute a state machine that is configured to change states based atleast on a dynamically adjustable counter, which is incremented when anarc, powered by the power supply, is detected.
 2. The power supply ofclaim 1, wherein the dynamically adjusted counter is decremented when anarc, powered by the power supply, is not detected.
 3. The power supplyof claim 1, wherein the state machine comprises two fan OFF states. 4.The power supply of claim 3, wherein the two fan OFF states include anidle state, and a wait_arc_time state during which the dynamicallyadjustable counter is incremented while an arc, powered by the powersupply, is detected, and the dynamically adjustable counter isdecremented while the arc is not detected.
 5. The power supply of claim1, wherein the state machine comprises two fan ON states.
 6. The powersupply of claim 5, wherein the two fan ON states include a fan_arc stateduring which the dynamically adjustable counter is incremented while anarc, powered by the power supply, is detected, and a fan_cooling stateduring which the dynamically adjustable counter is decremented while thearc is not detected.
 7. The power supply of claim 6, wherein when thestate machine is in the fan_cooling state and the dynamically adjustedcounter reaches zero, the fan is turned off.
 8. The power supply ofclaim 6, wherein when the state machine is in the fan_cooling state, andthe arc is detected, the state machine transitions to the fan_arc state.9. The power supply of claim 1, wherein the fan controller comprises amemory and a processor.
 10. A method comprising: detecting an arcpowered by a power supply; incrementing a counter while the arc is beingdetected; determining whether a value of the counter is greater than apredetermined threshold; when the value of the counter is greater thanthe predetermined threshold, turning on a fan to remove heat from acasing of the power supply; and when the arc is no longer beingdetected, decrementing the counter.
 11. The method of claim 10, furthercomprising: incrementing the counter while the fan is on.
 12. The methodof claim 11, further comprising: determining whether the value of thecounter is zero, and if the value of the counter is zero, turning offthe fan.
 13. The method of claim 11, wherein a rate of incrementing thecounter is different from a rate of decrementing the counter.
 14. Themethod of claim 10, wherein incrementing the counter is based on atime-element-schedule.
 15. A non-transitory computer readable storagemedia encoded with instructions that, when executed by a processor,cause the processor to: detect an arc powered by a power supply;increment a dynamically adjustable counter while the arc is beingdetected; determine whether a value of the dynamically adjustablecounter is greater than a predetermined threshold; and when the value ofthe dynamically adjustable counter is greater than the predeterminedthreshold, turn on a fan to remove heat from a casing of the powersupply.
 16. The non-transitory computer readable storage media of claim15, the instructions further including instructions that, when executedby the processor, cause the processor to increment the dynamicallyadjustable counter while the fan is on.
 17. The non-transitory computerreadable storage media of claim 16, the instructions further includinginstructions that, when executed by the processor, cause the processorto determine whether the arc is still being detected, and when the arcis no longer being detected decrement the dynamically adjustablecounter.
 18. The non-transitory computer readable storage media of claim17, the instructions further including instructions that, when executedby the processor, cause the processor to determine whether the value ofthe dynamically adjustable counter is zero, and if the value of thedynamically adjustable counter is zero, turn off the fan.